Chloroform and carbon tetracholoride are environmental and occupational contaminants with documented nephrotoxic potential in humans and laboratory animals. The primary site of kidney damage produced by these solvents is the proximal tubule. Although a significant amount of information has been obtained regarding the hepatotoxicity of these halogenated hydrocarbons, comparatively less is known concerning their nephrotoxicity, especially their action on proximal tubule cells. The proposed research will investigate the toxicity of chloroform and carbon tetrachloride using isolated human and rabbit proximal tubule segments in vitro. Proximal tubule segments will be isolated from human and rabbit kidneys using purely mechanical techniques that do not require the use of digestive enzymes. The first series of studies will examine and compare the concentration and time dependence of chloroform- and carbon tetrachloride-induced damage to human and rabbit proximal tubules in vitro. Other experiments will test whether those factors that are known to alter the toxicity of these halogenated hydrocarbons to liver also affect the severity of cellular damage to tubules. These studies will utilize various procedures to modulate tubular cytochrome P- 450 activity, intracellular cysteine and glutathione concentrations and lipid peroxidation in order to correlate changes in these parameters with halogenated hydrocarbon toxicity. The proposed research will combine cellular toxicology and biology methodologies to describe the effects of these halogenated hydrocarbons on the structure and function of human and rabbit proximal tubule cells in vitro. The proposed research will: (1) add greatly to our knowledge of the biochemistry of human proximal tubule cells, (2) improve our understanding of the mechanisms of chloroform and carbon tetrachloride nephrotoxicity, and (3) provide a basis for further research leading to meaningful predictive in vitro toxicity studies using proximal tubule segments.